In general, an air intake apparatus configured such that external gas can be introduced into an intake air passage is known. Such an air intake apparatus is disclosed in Japanese Patent Laying-Open No. 2011-80394, for example.
In Japanese Patent Laying-Open No. 2011-80394, there is disclosed an air intake apparatus for a multi-cylinder (four-cylinder) engine configured such that exhaust gas (EGR gas) of the engine can be partially introduced into an intake air passage. This air intake apparatus for a multi-cylinder engine described in Japanese Patent Laying-Open No. 2011-80394 includes an air intake apparatus body formed by integrating a surge tank and four air intake pipes connected to the surge tank. An EGR gas recirculation path (external gas passage) for introducing the EGR gas (external gas) is integrally formed on an air intake pipe member along the outer wall surface of the air intake apparatus body. Therefore, the EGR gas flows through the EGR gas recirculation path arranged on the outer wall surface of the air intake apparatus body, is branched into four, and thereafter is introduced (supplied) into the air intake pipes through inlets that pass through the outer wall and are communicated with the air intake pipes.